Complete the Addition Sentence - Sums up to 20
🧩 The missing piece! Time to use subtraction to find the hidden addend in these big addition sentences.
Do this: Read the concept below, then try the quiz or activity.
Concept
You know how to do this! But now the numbers go all the way up to 20.
🎯 The Subtraction Flip Strategy: If you have a missing piece in an addition sentence, flip it into a subtraction sentence! Example: 11 + ___ = 18 * Turn it around: 18 - 11 = ? * Let's subtract: 18 - 11 = 7. * So, the missing piece is 7! (11 + 7 = 18).
🎯 The Count On Strategy: If the numbers are close, just count up! Example: 15 + ___ = 19 * Start at 15. Count on to 19: "16, 17, 18, 19". * That took 4 steps. * The missing piece is 4! (15 + 4 = 19).
Try it
Find the hidden numbers!
Instructions: Use subtraction or count on to find the missing addend.
Problem 1: 12 + ___ = 17 * (Try counting on from 12!) * Answer: ___
Problem 2: ___ + 9 = 15 * (Try the flip! 15 - 9 = ?) * Answer: ___
Problem 3: 8 + ___ = 16 * (Wait! I know this double!) * Answer: ___
Problem 4: 14 + ___ = 20 * Answer: ___